1. Field of the Invention
This invention relates to stringed musical instruments. In particular, the invention relates to a stringed musical instrument with embedded digital signal processing (DSP) modeling capabilities.
2. Description of Related Art
Stringed instruments utilize vibrating strings to generate tones, and therefore music, since notes of music are merely particular tones. More particularly, a tone or note is a sound that repeats at a certain specific frequency. Throughout the world, various cultures have created a multitude of different stringed instruments such as: guitars, mandolins, banjos, basses, violins, sitars, ukuleles, etc., to create music. Moreover, with the advent of electronics, many of these stringed instruments have now been electrified to operate in conjunction with an amplifier and speaker. One of the most common stringed instruments in use today is the guitarxe2x80x94in both its electric and acoustic forms. The guitar is one of the most popular musical instruments in use today, and it spans a huge range of musical stylesxe2x80x94e.g. rock, country, jazz, folk, etc.
As previously discussed, the vibrating string of a stringed instrument generates a musical tone or note, which is in turn a function of: the length of the string; the amount of tension on the string; the weight of the string; the shape and thickness of the body of the stringed instrument, etc. Generally, stringed instruments, and the guitar in particular, include a body having a bridge to which each of the strings are respectively mounted, a neck having frets and a nut or xe2x80x98zeroxe2x80x99 fret, and a head having tuning pegs to which each of the strings are also respectively mounted. The length of the string is the distance between the bridge and the nut or xe2x80x98zeroxe2x80x99 fret. The amount of tension on the string is determined by the winding of the tuning peg which tightens and loosens the string (i.e. imparting tension) in order to tune the string to a certain note. In playing a stringed instrument, when a musician presses down on a string at a fret, the length of the string is changed and therefore its frequency is changed as well. The frets are spaced out so that the proper frequencies are produced when a string is held down at a given fret (and therefore the proper note is produced). However, it should be appreciated that not all stringed instruments have frets.
Looking at electrical stringed instruments, and utilizing an electric guitar as a particular example, to produce sound an electric guitar electronically senses the vibration of a string and generates an associated electrical signal and then routes the associated electric signal to an amplifier. The sensing generally occurs by utilizing electromagnetic pickups mounted under each of the strings of the guitar, respectively, in the guitars"" body and neck, at different locations. These electromagnetic pickups typically consist of a bar magnet wrapped with a coil of thousands of turns of fine wire. The vibrating steel strings of the electric guitar produce a corresponding vibration in the magnetic field of the electromagnetic pickup and therefore a current in the coil. This current represents the sound of the string at the location of the pickup and can be routed to an amplifier. Many electric guitars have two or three different magnetic pickups located at different points of the body and neck. Each magnetic pickup will have a distinctive sound, and multiple pickups can be paired, either in-phase or out, to produce additional variations. Thus, the electromagnetic pickup locations for particular types of electric guitars are a major factor in determining the xe2x80x9csoundxe2x80x9d associated with the particular electric guitar along with other factors. For example, classic xe2x80x9csoundsxe2x80x9d are associated with various types of GIBSON and FENDER brand electric guitars, as well as others.
In order to achieve a diverse array of well-known or classic types of guitar tones, a guitarist has traditionally been required to use many different guitars. Previous attempts have been made to allow a guitarist to obtain many different classic guitar sounds utilizing only one guitar, however, these attempts generally require modification of the guitar, non-standard guitar cabling, and extra equipment. For example, previous attempts have been made to emulate the different sounds of various guitars by processing the individual strings of a guitar by means of a multi-phonic pickup attached to a standard electric guitar that delivers string vibration signals to a separate outboard processing unit that utilizes digital signal processing (DSP) techniques. The processing unit performs DSP algorithms on the string vibration signal to simulate the sound of a particular well-known guitar. Unfortunately, this requires modification to the standard electric guitar, the use of non-standard guitar cables, and the use of a detached processing unit away from the guitar, between the guitar and the amplification system.
Moreover, previous DSP techniques, which are utilized to emulate the locations of the electromagnetic pickups along the string for the desired electric guitar to be emulated, are inadequate. This is because these DSP algorithms only emulate the electromagnetic pickups in one-dimension, in the horizontal xe2x80x98xxe2x80x99 axis along the length of the string utilizing simplistic modeling techniques. Further, the simplistic algorithms utilized completely ignore a critical aspect of the tone produced by an electromagnetic pickup, which is its distance from the string in the vertical or xe2x80x98yxe2x80x99 axis, referred to as the xe2x80x9cpickup heightxe2x80x9d. Thus, previous modeling techniques are insufficient to truly emulate the overall tone of the guitar in response to a string vibration signal, and therefore cannot truly emulate the sound of the desired classic electric guitar, or any desired electric string instrument to be emulated for that matter.
Embodiments of the invention relate to a stringed instrument with embedded digital signal processing (DSP) modeling capabilities. In one embodiment, the stringed instrument has a body and a plurality of strings. Each of the plurality of strings is respectively coupled to a pickup of a polyphonic bridge pickup. The polyphonic bridge pickup is used to detect a vibration signal for each string (e.g. when a string is played by a musician). An analog to digital converter converts the detected vibration signal of a string into a digital string vibration signal. Further, a digital signal processor is located within the body of the stringed instrument to process the digital string vibration signal. Particularly, the digital signal processor is used to process the digital string vibration signal such that the corresponding string tone of one of a plurality of selectable stringed instruments may be emulated. The emulated digital tone signal may then be converted to analog form to create an emulated analog tone signal for output to an amplification device. In one embodiment, a desired string instrument can be selected by a user from a plurality of different types of stringed instruments, which can then be emulated. Further, in one embodiment of the invention, one aspect of the emulation of the corresponding string tone of the selected stringed instrument is achieved utilizing a finite impulse response (FIR) filter.
In some embodiments of the invention, a user interface is located on the body of the stringed instrument in order to allow a user to select one of a plurality of selectable stringed instruments that can be emulated. A control processor may be coupled to the user interface to provide modeling coefficients from a memory to the digital signal processor for the particular stringed instrument selected by the user. Further, in one embodiment of the invention, a plurality of different types of guitar are selectable by the user.
Embodiments of the invention further provide for emulating the pickup height of an electromagnetic pickup (e.g. along the vertical or xe2x80x98yxe2x80x99 axis) for the corresponding string of an emulated electric guitar, as well as emulating the pickup location or placement (distance from the bridge) along the x-axis for the corresponding string of an emulated electric guitar. In this way, the overall tone of the electric guitar in response to a string vibration signal is emulated along both the xe2x80x98xxe2x80x99 and xe2x80x98yxe2x80x99 axis, and thus the sound of a selected electric guitar can be truly emulated. However, it should be appreciated that the xe2x80x98xxe2x80x99 and xe2x80x98yxe2x80x99 axis calculations can be determined for any type of electric string instrument in order to more accurately emulate the stringed instrument tone. Moreover, because the digital signal processor is contained within the stringed instrument, e.g. a guitar, extra equipment such as detached processing units for DSP processing, in between the guitar and the amplifier are not necessary, and further a standard guitar cable can be used. Thus, embodiments of the invention provide a much simpler and more accurate solution to emulating stringed instruments than in the past.